Turbocharging the Yan-clone L100: End of the Trail?

[Banzaibob]

The turbo project for this little bike is at best, disappointing. After fabricating a robust plenum chamber, adjustment of the governor and re-gearing the final drive I am about to conclude that it was all for naught. There are, however indications that I may be giving up too soon.

The turbo produces a solid 8-9psi of boost at the top of its rpm range and when the governor kicks in. The acceleration through the shifts is actually somewhat better than pre-turbo. It runs a little smoother on top and pulls slightly stronger through the lower rpms. The problem is, no matter what I do, I cannot get it over 53 mph. I even went back to the gearing I had pre-turbo. 4th gear will take me almost up to 55mph and when I shift to 5th, it hangs there for a while and starts slowing. I have adjusted the governor up and down, still no faster.

What I do know is that the turbo is providing solid boost seemingly throughout the usable rpm range. 35mph in 3rd gear, medium throttle produces anywhere between 4 and 7psi (depending on conditions). It "sounds" as if it is in a high state of tune and does not appear to be generating that more more heat. It runs quieter and smoother, just not faster. The ambient air temp today was 32º. The engine was thoroughly warmed up however. Would the air temperate put that big a damper on performance?

Basically what I would like to know is if anyone has any ideas as to make this thing go faster? I am at the point where I'm considering taking the turbo off and going back to normal aspiration. I have a Honda SOHC 750 project that I could use this turbo on. I'd RATHER use it on the diesel though. Ideas? Discuss?

[gilburton]

It would be interesting to get this bolted to a bike with similar engine and cvt to see if it made any difference??
Just a thought as you say it responds until you get in top gear??

[Banzaibob]

The short answer to what it would do with a CVT is probably 53mph. I have used several different gearing combinations varying as much as 12% reduction in final drive ratios. Still no difference. I have adjusted the governor to the point that it is basically no longer limiting top speed and still the same result. I imagine that I could advance the timing, get heavier valve springs, etc. to try and make the engine rev higher but eventually that would be counter to what I want I originally had in mind. I would probably ruin the engine in the process.

I have/have had several bike engines that I have built with performance in mind, usually SOHC CB750's. Most people build these engines to zip through the 1/4 mile but they don't last long. I usually try to build them with the idea of doing 90mph all day long across Kansas in 100º heat. Even though this Yanmar clone (?) is built very robust, I am wondering if there is any reliable way to squeeze just a little more performance from it. Unless someone has another solution or I have made a mistake I would have to assume that turbocharging is not necessarily the correct path.

[gilburton]

Yeah I suspect you're just making the engine breath easier but it's still only 10hp so you're only going to get the speeds you say.
What about a small supercharger instead of a turbo??
Over here we used to have Shorrock superchargers and they were regularly fitted to small cars and drag bikes years ago. They used to come with fitting kits to suit your car. No mods were required to the engine and I know they worked well as I fitted one to my early mini. Instant bolt on power
http://www.thefang.co.uk/shorrocks.htm
Do you have anything similarly compact over there??
http://www.shorrocksuperchargers.co.uk/

[Banzaibob]

We have tossed about the idea of using a smog pump as a budget supercharger. It is a tempting idea but as you say, it is just a 10hp engine and asking to do more may result in more futility. I actually spoke to an engineer at U.S. Yanmar service center last year. He liked the idea of a diesel motorcycle but when asked about turbocharging was rather doubtful (not completely doubtful) about the prospects. His concern was mostly with long term reliability. Given that these engines are designed to run at a constant speed, year in and year out, it's easy to understand his concern.

Unless someone can point to a specific mistake that I made our come up with an elegant solution that will give me an extra 15-20mph then I believe that I will return it to its original build state and try to be satisfied with that. It actually makes an outstanding around town bike. It has sharp, quick handling, decent brakes, fair load capacity and as long as you can live with speeds of 55-60mph or less will get you where you want to go. I was always stunned by the mileage figures of 150mpg.

Right now building it past its present point is not the solution. I cannot keep dumping money and time into this bike. I have too many other projects that will pay off. My solution? Keep asking people for their advice on how to make this turbo work with this engine to give me 20 more mph. Yesterday a friend suggested an intercooler. I said that ambient temperature was 32º, I doubt that the intake charge was too hot. Which leads me to another question; I have not tested this configuration in temps above 45º. How much of a difference should I see at 80º?

[gilburton]

I think the only route you can go would be a twin engine around 20hp if you want the extra power/speed out of a diesel industrial engine?? You should get 60/65mph. You could sell on your existing engine to get back some of the cost?
If you avoid the V twin and go for a parallel twin it should slot in quite easily as you appear to have engineering facilities?

[toyotaracer9]

You still dont get it, just because it makes boost doesnt mean its in the efficiency range. It is lagging causing it to be restrictive , the intake plenum is big enough to flow 200hp to a 4 cylinder. Their is no need for a plenum like that and the reed cage is useless they have 1000hp 4 cylinder engines out there that flow all of the air through the turbo all of the time . That little turbo is made to flow over 100hp

[Banzaibob]

I do get it. However this engine's performance has improved, narrowly, but improved nonetheless. It's low and mid rpm response is greater and smoother. It now pulls hills in 2nd and 3rd gear with modestly better performance. My problem is that it is not doing what I wanted it to do; pull better at high speed in 5th gear. I understand that the engine is over sized for this turbo. In fact, unless I, or someone can come up with an elegant fix for this specific combination I have a couple of 750 or 1000cc gasoline engines that this turbo is going to eventually find its way on.

On this discussion board there appears to be no shortage of people familiar with this specific engine and people with this specific turbocharger. An earlier poster suggested a CVT. With such a transmission I assume the engine would simply rev its way to a point of efficiency. I simply can't do that at this point. I fully understand that I am trying to make a silk purse out of a sow's ear. I would suggest to you however that I am getting closer all the time. I am not asking for racing performance and if it is not to be, that's fine. Before I relegate this turbo to gasoline I'm thinking that perhaps modest tweaks may push me incrementally in the right direction.

For instance, when I added the reed valve it woke up it's low end response. What other changes are left to me?

[toyotaracer9]

So in low and mid range, is it using the reed valve?

[Banzaibob]

In low, yes. In mid range, at medium throttle settings (25-35mph, 3rd gear) it is generating 4-6psi of boost.

[Banzaibob]

I should elaborate a little further. As I shift through the gears, I can easily take it up to maximum rpms. I have even adjusted the governor so basically the governing action is bypassed. At the upper rpm range in lower gears it can easy generate 9-10 pounds of thrust. Revving it that high is, of course unnecessary so I shift usually when the engine starts to sound stressed. At that point boost varies in between 5 to 8 psi depending on conditions of course.

I would guess that if this was a gas engine with 5000 more rpm left in it's rev range I would be smoking tires and such.

[thundercougarfalconbird]

you may want to think about another problem, what happens to the static compression ratio of 22:1 or 22.5 :1 when you add 9 or 10 pounds boost?????

not many diesels run that high of a compression ratio when they have turbos

http://www.rbracing-rsr.com/compression.htm

you have to rethink the engine and make all kinds of mods to work, and an intercooler is a MUST.

im not giving away all my secrets on here but will point you in the correct direction

[BertTrack]

Have you by any change tried a shorter gearing? I mean maybe gear it so the new 5th is a little more than your current 4th. That way you may be able to reach your intended topspeed. Although maybe the gap between 4 and 5th is simply too big? (even when you gear it shorter)

[toyotaracer9]

There is no need for an intercooler or internal mods for this application especially in 30f temps. I have 4 personal vehicles with homemade turbos and have turbo quite a few friends cars, My wifes car has stock internals running 7lbs boost for 142k miles My truck has stock internals running 7lbs and has 200k miles neither have intercoolers so trust me its not a must have on low boost but sure it would make more power with one. I also have another 4cyl. truck running 20lbs making around 400whp sure it has an intercooler and internals . My diesel bike is making 10lbs boost on stock internals and ran 85-87mph with no intercooler but IAT were 160-170f so Im in the process of installing an intercooler ambient temps down here are in the 90s 7 months a year.

[thundercougarfalconbird]

toyotaracer, are your cars gas or diesel?

the engines we are using have many different challanges compared to a car engine, cam profiles rpm ranges being different, maybe the problem is the turbo is too small and there is not enough heat, volume and pressure being made to powr the turbo past the boost it makes, its almost like it stalls, too much dead space with a single cylinder 4 cycle engine at a slow rpm, these turbos work well on the v twin but do require an intercooler, i know this for a fact, they will work well for about 15 or 20 minutes and after it gets hot they dont work well, improper idle and poor power, the air is so hot there is no power left in the hot air, but this is all experimental so it is left for each of us to figure out what works. you cant have an engine with a 22.5:1 compression ratio and add 9 or 10 pound boost and expect it to work well, the compression ratio ends up well over 30:1 and you start to fight making power, but what do i know.

[Banzaibob]

So please help me understand here because even though I am incredibly hansom, I'm not very smart.

Is it thundercougarfalconbird's contention that with 8-9psi of boost and 19:1 compression, the effective compression ratio is more like 28:1? ....and because the effective compression ratio is so high the engine DOES NOT have enough effective inertia to overcome such a high compression ratio? If I was to lower the compression ratio via shims or whatever means, what comp. ratio number would I be looking for? i.e.16:1, 15:1? Also I would think that in testing this setup in ambient temperatures close to the freezing mark, an intercooler would not make a significant difference, is this NOT true? Would I be adjusting for seasonal differences? Discuss, please.

Also, since it appears that I have confused boost with actual CFM, 1) can this rhb31 turbo be adapted in some/any fashion that would give me good results and if not 2) what type of turbocharger WOULD work effectively with a small displacement, low expectation diesel engine?

[toyotaracer9]

I think you meant the engine is too small to create enough heat energy for the turbo and I agree 100% I was just trying to clarify that the items you mentioned arent going to get his engine to spool the turbo any better. The engine is putting 8whp to the ground @3600 rpm and probably no more than 6whp when it is shifted into 5th gear so the engine isnt flowing enough air to make the wastegate open with 8whp @ 3600 it has no chance of flowing enough with 6whp @ lets say 2800rpm.

[Banzaibob]

Let me draw you a parable. Back in the day, when a kid could actually afford to race motocross I used to take my 2-stroke piston port engines and trim 1.5mm off of a intake side of the piston skirt. This totally robbed my low end power but now the thing would rev to the moon bringing all sorts of horsepower with it. I used to also slot the cam chain sprocket holes on my small Honda's and advance cam timing basically doing the same thing. Basically those "fixes" didn't fundamentally change things, they simply shifted the power band up to a point that more air was moving at higher speeds. If Thundercougarfalconbird is talking about a solution that is not outside of my skill level, I'm going to try it. If fabricating some sort of intercooler or shimming my cylinder head will give me 20% more on top then I'm good. If anyone knows of a turbo that WILL work, I'm good.

By the way, so far I've tried changing the final drive a couple of times. 53mph seems to be the limit regardless if it is revved out in 5th or chugging along in 5th (or 4th for that matter).

For what it is worth I would not mind revisiting the idea of variable injection timing.

[toyotaracer9]

By the way, so far I've tried changing the final drive a couple of times. 53mph seems to be the limit regardless if it is revved out in 5th or chugging along in 5th (or 4th for that matter).

I would think the reason 53mph is the constant speed is because the engine is making close to the same hp at all of the rpm you were changing the final drive to?

[Banzaibob]

With the present rather tall gearing it maxes out in 4th gear at around 50-53mph. Shifting into 5th, it sort of sits there eventually succumbing to a mild incline or headwind. In 5th gear it will actually pull from say 40mph all the way back up to 50 or so. With the shorter gearing it revs in 4th gear up to about 45mph. Shifting it into 5th gear slowly brings it up to, you guessed it, 50-53mph. I don't have a tach although I'm thinking about borrowing one if I get into this turbo thing any farther.

Before the turbo it would grind down a flat highway at a solid 55mph with downhills giving me 60+mph and uphills 45.

It still begs the question; all this bike needs is an extra 10mph or so. Turbocharging with this turbo is presently not the answer. Does someone make a turbo that is the answer? Have I explored all of the options that would make this turbo work (intercooler, compression reduction)? Is there another performance mod for a diesel engine of this size/type?

[Banzaibob]

Another question; since this turbo is effectively running off of heat energy, would increasing the exhaust temperature, per se, increase the turbo's efficiency? Is using a hotter burning fuel an option? Kerosene? Naptha? Mothballs?

[toyotaracer9]

Another question; since this turbo is effectively running off of heat energy, would increasing the exhaust temperature, per se, increase the turbo's efficiency? Is using a hotter burning fuel an option? Kerosene? Naptha? Mothballs?

Yes, but I dont think you will ever get it into its efficiency range. On properly sized turbo engines you can spool the turbo 500 rpm earlier after the turbo is hot from back to back runs.

[Banzaibob]

I think that I'm going to fit a nice conventional tailpipe to it, put the air filter back on the manifold and fix the left front turn signal.

[larkout]

I'm getting into this a little bit late, so this might be a bit of a ramble.
A hyper-mileage, highway capable dirt loving scrambler is becoming somewhat of a grail for me. Theres a launtop 10 hp unit on my porch, a vz21 under the desk, and an xl 250 rolling chassis down the street... I was feeling pretty set up until running into these threads. I'm still of the opinion that this should all work out fine. I am beginning to feel like Hercule Poirot, perhaps even more mysterious than the running of these engines is that whenever somebody gets one in running condition the other end of the line goes dead.
First, I think that this turbo (rb31/vz21) is great for this engine (yanclone 10hp). If you do the math for how much air you need to flow to create the hp you (reasonably) expect under a rational amount of boost (7 psi seems great) and then consult the compressor maps, this combination is in green light territory. Its not in the most efficient heart of the map, but its in the design range. Diesels in general want a lower boost, higher flow, lower rpm turbo scenario than a gas motor, this points to having a realatively oversized turbo compared to an equivalent gas motor. We got that! The general downside of an oversized turbo ( or its it an undersized engine?) is turbo lag, the time it takes for the turbine to spool in response to increased exhaust pressure and consequently build effective boost pressure/ air flow is longer. Stoplight to stoplight this will feel like you're working the accelerator with a rubber band, pulls slow, pulls slow, pulls ok, and then whoa its really pulling. But we're talking about a more steady state situation, cruising down the highway. Also, turbo lag = bfd.
When I actually get mine together I'll probably make a header the same diameter as the exhaust port, shoot for a volume of 2-3x displacement, but priority is going to go to turbo placement. I think that a plenum to balance out pressure and intake pulses is a always a good idea... I think what you have going on there is probably alright.
Does it smoke at the top of 4th gear? Are you building as much boost in other gears as when its bogged out in 5th?
You're building boost, you're getting more air in the cylinder, you have apparently enough fuel to match.... so there should be more power not smoke...
To me, this all says that you're just not burning the fuel that is getting pumped in. Some paraphrasing to get us all on the same page: Once the fuel is injected there is some lag time before much combustion happens, this has to do with the fuel flammability and temperature inside the cylinder. Cylinder pressure / heat are little affected by this phase of the combustion. This bit of lag (timewise) is pretty constant through out the speed range of the engine. Next, the fuel that had been injected during the first phase begins to ignite (the injection event is still happening). The fuel stratified into little droplets and burn from their surface. The speed of this phase is dependent on the fineness of the sprayed fuel droplets, cylinder charge temperature, fuel characteristics, and air turbulence. Remember the droplets are burning from their surface, they need a wind to strip the byproducts of combustion, provide fresh oxygen, and continue burning efficiently. In the third phase of the combustion, cylinder pressure and temperature have increased enough through the actions of phase 2 that newly injected fuel is ignited immediately.
Fun! I'm thinking about that second phase. And keep in mind the context, high rpm which means less time to burn. Fuel burns, thats what it does, it just not burning enough, not quickly enough. The increased cylinder load and pressure ( and heat) from the turbo should be a good thing here. You can advance the injection timing to get more time to burn ( I would try it out, see how bad you can make the idle). You can try to run a quicker burning fuel.
These ideas are in the direction of a solution but might not be at all practical- Higher injection pressure might help atomise the fuel better. To a smaller extent the extra fuel velocity has the same effect as increased turbulence in the cylinder (air moving over the fuel droplets), contributes to actual air turbulence, air-fuel mixing, and pushes fuel deeper into the nether regions of the chamber. I don't know, sprays slow down pretty quick, but then our fuel system is running relatively low pressure. I certainly want to look into dialing up the injection pressure.
Better spray from the injector. Check out 'home made injector pop testers'. Seems the best way to see what is going on with the injectors. Maybe they pop at too low of pressure? Maybe they spurt more than spray? I also want to look into other injectors, maybe find a finer spray or different spray pattern... this is probably less feasible.
Other things I wonder are if you can get a different injection system altogether? Maybe just to get higher pressure, but even better would be adjustable timing, and some kind of multi-phase injection event...
My odds are on advanced timing and increased injection pressure.
O boy.

[gearhead1951]

I am a US navy veteran , retired Engineman 1st class . That means I have 20 yrs experience with marine main propulsion diesel engines !

If your Injector is dirty or your pump is compromised you will not get any improvement with a turbo or supercharger .

Make sure your pump is as good as it can be , upgrade if possible . Pop testing your injector is only of use if you have the factory data to to compare you results to !

If you know how or can find a tutorial , rebuilding your injector and pump to factory specs is a good idea . A better idea is to rebuild them to the specs that are required to support use of the 'charger !

Or swap them for units that will do the job !

[Banzaibob]

This project was built with an engine that had sat for 8 years. Even though it was not seized it needed numerous parts. I had to replaced the cylinder head and piston (cracked, not seized), the cylinder head studs, the fuel pump and the injector. All parts were brand new. I later got another fuel pump with a solenoid shut off. It ran, and has ran like a champ from the git-go. I have pretty high confidence in the engine and all of it's components.

When I first envisioned this turbocharging thing I was expecting (all other things being equal) about a 25% boost in performance. Realistically it has cut my power by 5-10%.

As to larkout and his future build I can only say good luck. I am convinced that this engine is simply not a good platform to turbocharge. As I stated in an earlier post, there are a lot of people who post about the progress of their turbo build. The posts are usually optimistic. They appear to reach a tipping point however and all of a sudden the thread goes dark.

On my bike I put in a fuel stop to prevent overfueling (per-turbo days). I could be riding along and actually feel the point where adding more fuel was starting to give me drag. Of course it would smoke like a sumbitch. After minimal trial and error I got it set to a point where it appeared to have maximum efficiency. When I installed the turbo I backed it out all of the way to make sure it was getting all of the fuel it needed. The engine behaves pretty much the same way in top gear; you can give it fuel to a point where you "feel" it overfueling and it starts to drag. It also is giving me clouds of black smoke. I simply cannot imagine that it is NOT getting enough fuel.

I think that one gentleman's comment finally got through to me when he stated that I was confusing boost for CFM. My original build intent was reliability followed by reliability. If I am visualizing this correctly, this turbo will start generating lots of power at about 5000rpm. I don't think that there is anyway to get 20,000 miles out of one of these engines operating at that speed and above. My "prime directive" is out the window at that point.

It also appears that the transmission also plays an important part in this equation. Many build their bikes with a CVT. In many ways this is indeed a superior platform for turbocharging. The engine will simply rev to a point where there is boost and increased performance and in essence, the transmission will oblige with infinite ratios. Using a 5speed manual motorcycle transmission limits the ratios that one can utilize. The trade off of course is that a manual trans gives much better feel and connectivity to the road. Also aesthetically it is far and above (only my opinion).

All of these suggestions and computations are all well and good. The fact remains; pouring blood and treasure into an engine that is designed to give 10hp at one speed for years and years to try to make it into something else is just not practical for me. I think that a better candidate for the thrust of this entire discussion would be one of the larger 25hp 2 or 3 cylinder engines out there. I have a couple of old '76 Honda Goldwings that are begging for a diesel conversion.

[larkout]

How is the power in the middle of the range? Does it push better with turbo up a hill at say, 2500 rpm?
This is getting to be a tough riddle. It may be time to walk away, but without a clear answer I myself can't start putting nails in the coffin.

[Banzaibob]

Mid-range power appears marginally better. When I first started I did not have a reed valve in place and I thought that it was weaker in the low end. The reed valve helped that problem significantly. Since I do not have access to a dyno I have to rely on seat-of-my-pants dead reckoning. One of the things that I did when I first built the bike was retard the injection timing so it would not knock so much at idle and low rpm. It made the bike respond much better at the stop light. Hhowever at high rpms in lower gears it would misfire. When I installed the turbo I removed the shim and went back to the stock injection timing settings. With the turbo it knocked less at idle and mid-range. The turbo also makes it much quieter, in essence it is a rotary muffler.

Overall I would have to say that WITH the turbo, it pulls hills a little better in the lower gears. Is this slight increase in mid range/speed worth the sacrifice of 10mph of top speed? For me, the answer would have to be no. I agree that the problem is a tough riddle. I want to believe that these slight performance increases would extrapolate to overall higher speeds. The entire spectrum of results is quite counter intuitive. I imagine that just one more competent added to the mix would put me over the top. Unfortunately.....

I am probably going to take it all off and go back to stock timing. At stock it would generally do highway speeds slowing on the hills and headwinds. As far as advancing the timing goes, the low end and mid-range knock is simply wicked, high end performance is great. It's got to live its life reasonably happy through all of the rpm range.

[gearhead1951]

First , Just 'cause something is new and you opened the box dont mean its not screwed !

A pop test WILL tell you if you are getting proper atomization or not (be very carefull here , an injector shoots that deisel out at velocities that will penetrate your skin and get it into your blood) !

Second , do you know what your boost is at all rpm's as you are riding ? You may have covered this already but if so I missed it !

If you have good boost at wfo throttle and at top speed and are not getting any improvement in performance then I am absolutely baffled !!

[Banzaibob]

I did not do a pop test but I did stand back and cycle it through with the starter motor to see if everything worked. It threw a big beautiful 4 pedal flower of diesel mist. Once installed it worked flawlessly.
When it is maxed out in 4th gear (about 53mph) I can only guess that it is running at 3600-4000rpm. It is generating 9psi of boost at that point. Shifting into 5th gear, the boost drops to about 6-7psi and I can only guess that it is about 3000rpm. It then starts to fade, gradually slowing down to about 48-50mph and staying there. You can shift back into 4th and get your speed back up if you wish.